Turbine stator assembly



oct. 16, 1956 D, G. ZIMMERMAN 2,766,963

TURBINE STATOR ASSEMBLY v Filed Nov. l. 1952 2 Sheets-Sheet 1 52 /f J0 /5 ff( ZZ i /f i fa /Z if( k ya 54 Z i 7 ff 7 Inventor a/za//QW/Wff//fm Attorn evs Oct. 16, 1956 D. G. ZIMMERMAN TURBINE STATOR ASSEMBLY 2 Sheets-Sheet 2 Filed NOV. l. 1952 uUnited States Patent O TURBINE sTAToR ASSEMBLY Donald G. Zimmerman, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 1, 195.2, Serial No. 318,177

7 Claims. (Cl. 253-78) This invention relates to elastic uid turbines for high temperature fluids and more particularly to a means for supporting the stator vane assemblies of an axial flow turbine in the external casing of the turbine.

A known type of multistage axial flow gas turbine includes a plurality of external casing rings that are bolted together and a plurality of stator vane assemblies located within the external casing and peripherally flanged thereto for support. The stator vane assemblies tend to expand more than the external casing so they are segmented along planes extending generally in an axial direction. Clearance is provided between the segments so that they may expand peripherally without deforming the external casing and yet maintain the desired minimum clearance between the turbine rotor and the stator vane assemblies. The stator vane assemblies have been located by radial dov/els that threaded through the external casing and extended into annular bosses on the segments prior to this invention.

The object of the invention is to provide an improved turbine casing construction including an improved means for locating the stator vane assemblies in the external casing.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the invention is clearly shown.

in the drawings:

Fig. l is a longitudinal section of a portion of a multistage axial iiow turbine constructed in accordance with the invention;

Fig. 2 is an enlarged partial section illustrating the joint locating of the rst and second stator vane assemblies to the external casing by a common key;

Fig. 3 is an enlarged partial section illustrating the joint locating of the third and fourth stator vane assemblies to the external casing by a common key;

Fig. 4 is an enlarged partial section illustrating the intel-flanged interconnection between the iirst and second stator vane assemblies and the external casing;

Fig. 5 is an enlarged section illustrating the interanged interconnection between the third and fourth stator Vane assemblies and the external casing;

Fig. 6 is a perspective elevation of a iirst and second stator vane locating key;

Fig. 7 is a perspective elevation of a third and fourth stator vane locating key;

Fig. 8 is a partial plan view of the turbine casing having portions of the external casing members partially broken away to illustrate the segmented nature of the stator vane assemblies and their keying arrangement; and

Fig. 9 is a partial elevation view of the iirst stage stator ring taken along the plane indicated by the line 9 9 of Fig. 8.

Referring now to the drawings in detail, the turbine assembly comprises two major components, a turbine rotor assembly and a turbine casing assembly. The turbine casing assembly includes an outer casing structure 2,766,963 Patented Oct. 16, 1956 ICC that encircles the blade system of the turbine and an inner casing structure supported thereby and defining therewith the inlet and exhaust portions ofthe turbine and providing bearing support for the turbine rotor assembly. The outer casing structure includes arigid multipart external casing structure and a segmented, relatively exible, stator-vaned internal casing structure secured thereto. The turbine rotor assembly includes a bladed drum built up from alternating bladed disks and nonbladed spacer disks. The forenoted turbine construction may be conventional and therefore only so much of the structure as is necessary to enable one skilled in the art to understand the invention is illustrated. The invention is illustrated as applied to a four-stage turbine, but it should be realized that it may be applied to as many stages as may be desired.

A rear casing 16, an intermediate casing 12 and a forward casing 14 which comprise the primary structural components of the turbine casing assembly are bolted together at 16 and 18, the rear casing 10 supporting an exhaust casing structure 20 by bolts 22. The exhaust casing structure 20 includes outer shells 24 and 26 and inner cones 28 and 30, the inner cones and the rear turbine bearing being supported from the rear casing 10 by radial struts (not shown). The inlet casing st-ructure 32 includes the forward casing 14 and an inner casing 34 and a forward bearing support plate 36 supported therefrom by radial struts (not shown). The turbine rotor assembly 3S includes blade disks 4i? and spacer disks 42 suitably secured together for rotation in the turbine casing in the usual manner. The outer casing structure includes four stator vane assemblies supported from the casings 10, 12 and 14 by peripheral tongue and groove structure to be described.

The stator vane assemblies form the fixed blading for the turbine and an internal casing structure forthe turbine casing assembly. The stator vane assemblies include the outer shroud rings 70, 76, 82 and 88 and the inner shroud rings 52 secured thereto by the stator vanes 54, the first stage inner shroud ring being additionally supported by the inner casing 34 and the remaining inner shroud rings serving as gas seals between the blading stages of the turbine rotor.

The turbine unit is assembled from rear to front as will be described. The external casings 10, 12 and 14 are formed with peripheral tongues 60, 62, 64. and 66 that extend axially to support the stator vane assemblies. The fourth stage outer shroud ring 7i) is formed with a peripheral .grooved flange 72 that embraces the tongue 62 and a peripheral flange 74 received in the groove formed by the tongue 60. r[The third stage outer shroud ring 76 is formed with a peripheral tongue 78 received in the groove of the ange 72 and a peripheral fiange 80 received in the groove formed by the tongue 64. The rst stage outer shroud ring 32 is formed Witha peripherally grooved flange 84 that embraces the tongue 66 and a peripheral ridge S6 that bears against the interior of the forward casing 14. The second stage outer shroud ring 88 is formed with a peripheral tongue 90 received in the groove of the tiange S4 and a peripheral ange 92 received in the groove formed by the tongue 64.

A considerable temperature differential exists between the shroud ring assemblies and the external casing i0, 12 and 14 during turbine operation. The temperature differential tends to cause deformation of either or both the stator vane assemblies and external casings so the stator vane assemblies are segmented along planes extending generally longitudinally of the turbine axis, and clearance spaces 94 (Figs. 8 and 9.) are provided between the segments so that they may expand peripherally ratherthan radially (the outer shroud. rings being relatively exible with respect to the casings 10, 12 and 14). The tongue Y 3 and groove structure interconnects the external casings and the outer shroud rings and constrains the stator vane assemblies radially so :that they remainproperly centered at all times. The individual segments of the stator vane assemblies are located circumferentially and maintained in their proper circumferentiallocation by keys 9.6 and 93. Y

' peripherally from their center.' The clearance spaces 94 accommodateY such expansion.V it should be understood that the degree of segmentation `of stator vane assemblies may be Yvaried if desired. VThe torque reaction'from'the stator vane assemblies is transferred to the casings 10, 12 and 14 by the keys 96 and 98. The tongue and groove interconnections are .slotted as shown' in Figs.

2 and 3 in an axial direction to receive'the keys, and Vit should be noted that the keys are located wholly within the outer casing structure, i. e., they do not extend outside the casingsy 10, 12 and 14 nor inside the outer shroud rings "70, 76, S2 and 8S. Each key 98V is received in aligned complementary slots Vthat traverseV the casing tongue'66, the iirst stageY shroud ring flange 84 and the second stage shroud -ring tongue 90. Each key 96 is received in aligned complementary slots that traverse Ythe casing tonguef62, the lthird stage shroud ring tongue 78 and the fourth stage shroud ring ange 72.

TheV assembly of the turbineVv unit is accomplished as follows: Theexhaust casing structure 20 is mounted vertically in a suitable fixture. The rear casing is then bolted to the exhaust casing Ystructure 20. The turbine rotor assembly is next lowered by an overhead hoist into the forward portion of the rear casing 10.

The fourth stage stator segments are then placed in position and the turbine rotor assembly is lowered further into'the rear casing V10. second stage stator Ysegments Yare then inserted between the first and second blading stagesrof the rotor andthe third stage stator segments are inserted between the second and thirdV blading stages of the rotor; `and the.V turbine rotor, with statorY segments in place, is loweredinto its nal location in the rear casing 10 so that the ange 74 engages the tongue 60. The-keys 96 are then .inserted in the slotted t tongue and groove interconnectionsrof the third and fourth stages so that these stages are keyed together.

VThe intermediate casing 12 is then slipped Vover the second andthird stage stator segments so thatV the tongues 62 and 64 engage the flanges 72 and 92 respectively, the slots in the tongue 62 engaging the keys 96 to key the third VYand fourth stage Vstator segments to the intermediate casing 12. The intermediate casing 12 is then bolted to the rear casing 10. The keys 98 are next inserted in the slots in the Atongues 66 and "90 and the inlet casing structure 32, with its first stage stator segments in place, is then slipped into position with the grooved flange 84 engaging the tongues 66 and.9v0 andV the keys 98 being received in the slots in the grooved flange. The inlet casing structure 32 is then bolted to the intermediate casing-12 Vto form the complete turbine unit.

Advantages attained by utilizing the keying arrangement'of the invention in preference to the Vusual radial dowels are the elimination of bores through the casing for mounting the dowels and Vthe subsequent possi- Y bility ofrmotive fluid leakage therethrough, the elimination of dowel receiving bosses on the segments, easier assembling ofthe turbine, and areduction in the numberV of segment locators required, i. e., one key serves to locate two segments Whereas two dowels were previously required. Y

While the preferred embodiment of the invention has been described fully in order to' explain the principles of the invention, it is to be understood'that modifications in structure may be made by" the exercise of skill in the art within the scope of the invention, which is not to be regarded as limitedby the detailed description of the preferred embodiment.r Y 'Y l claim:

l. An elastic fluid turbine comprising an annular casing,.a stator vane shroud ring disposed in said casing,V

peripherally extending Vtongue and grooveL structurer-.on

said casing and said'ringfor mounting -said ring in VsaidV casing, Va plurality of peripherally spaced slots Veach traversing said tongue and groovestructure, .and keys located in said slots of said tongue and groove structure for circumferentially locating said VringV in said casing.

2. A multistage elastic fluid turbine comprising an annular casing, a pair of stator vane shroud rings disposed 3. A multistage elastic iiuid turbine comprising an an-Y nular casing, a pair of stator Vvane shroud rings disposed in said casing in abutting end to end relation, means for Y mounting said rings in said casing comprising a peripheral tongue formed on saidY casing andY a peripheral tongue formed on the abutting end of one of said ringsY cojointly received ina peripheral groove formed in'the abutting end of the other of said rings, a plurality of pef .v

ripherally spaced slots each traversing said tongues and said groove, and keys Vlocated'in said slots of said tongues and said groove for circumferentially locating said ringsV in said casing. Y

4. A multistage elastic fluid turbine comprisingan annular casing, a pair of stator vane shroud rings disposed in said casing in abutting end to end relation, means Vfor mounting said rings in said casing comprising a peripheral tongue formed on said casing and a peripheral tongue formed on the abutting'end of one ofY said ,rings coiointi' ly received in a peripheral groove formed inthe abutting Vend of the other'of said rings, a plurality of peripherally spaced slots each traversing said tongues and said groove,

and keys located in said slots of said tongues and said groove for circumferentially locating said rings in said casing, said keys being wholly disposed Within said casing.

5. A multistage elastic fluid turbine comprising an annular casing, a pair of annular members disposed in said casing in abutting end to end relation, each of said members being parted V.substantially longitudinally of the turbine to provide a plurality of arcuateV stator vane supporting segments, the `abutting ends of said members being peripherally joined to eachother and to said casing by a tongue and groove connection to support said members in said casing, a plurality of peripherally spaced slots each traversing said connection, and keys located in said slots of said connection for circumferentially locating each of said segments in'said casing. Y

6. A multistage elastic uid turbine comprising an annular casing, a pluralityfof arcuate stator vane supporting elements disposed circumferentially in said casing to form a pair of stator vane `shroud rings, said rings` being disposed in said casing in abutting end to end relation, means for mounting said rings in said casing comprising a peripheral tongue formed on said casing and a peripheral (tongue formed on the abutting end of one of said rings ing a pair of said lements.

7. A multistage elastic fluid turbine comprising rst and second annular members having abutting ends secured together to form an external casing for the blade system of the turbine, said first member having an internal flange on its abutting end that underlies the inner surface of the abutting end of said second member in radially spaced relation, a set of rst arcuate stator vane supporting elements disposed circumferentially in said iirst member, a set of second arcuate stator vane supporting elements disposed circumferentially in said second member, said first and second elements being in abutting end to end relation, said second elements having their abutting ends grooved to receive said ange and the abutting ends of said first elements for mounting said elements in said casing, said flange and said abutting ends of said elements having a plurality of peripheraliy spaced transverse slots, and a plurality of keys each disposed in one of said slots fer Circumferentially locating said elements in said casing.

References Cited in the file of this patent UNITED STATES PATENTS 

